Sputtering is a coating process involving the transport of a material from a source (target) to a substrate. The process takes place in a reduced pressure atmosphere of argon gas (a partial vacuum). Particles of the source material are dislodged from the target surface by bombarding the surface with argon gas ions. These dislodged particles travel through the vacuum and are deposited on the substrate as a thin film. Sputtering technology is of great use in the semiconductor industry.
In the past, pure metal powders have been used in the manufacturing process for sputtering targets. Due to the limited useful life of sputtering targets, however, recent efforts have been made toward reducing the costs of manufacturing by recycling used targets and replacing the expensive pure metal powders with the recycled material. In the area of tungsten-titanium (W/Ti) thin film coatings, efforts have been directed to the recycling of used Ti targets.
In one process, used Ti metal is converted to titanium hydride (TiH.sub.2) powder, typically by adding hydrogen in a furnace at a high temperature while agitating the metal. The Ti powder is then dehydrated in the same furnace in one continuous operation. This recycled Ti powder, having no hydrogen content as a result of the dehydration step, can then be used with pure W powder for the subsequent manufacture of a W/Ti sputtering target. A second process similarly involves converting used Ti metal to TiH.sub.2 powder and dehydrating the powder to Ti powder, but instead performs these steps in two separate operations, involving an intermediate transfer of the material from one vessel to another.
The first process, in which a single operation is performed, has the disadvantage of being very time consuming, resulting in high production costs and delay in the manufacturing of the final target product. The second process not only has the disadvantage of being very time consuming, but also increases the risk of material contamination during the transfer of the material. Furthermore, the dehydration step in these processes involves the rotation and agitation of the powder in a rotary furnace, which has a molybdenum lining. The rotation and agitation wears and abrades the lining, causing contamination of the Ti powder. Targets manufactured from the recycled Ti metal are also frequently rejected due to high gas (oxygen) content.